Advantages
CO2 is non-conductive and non-corrosive. It reduces the oxygen available to fuel the fire. It is used against fires involving live electrical appliances such as toasters, computers and switchboards. Because its a gas, it is able to get in and around objects and confined spaces to smother the oxygen fueling a fire. Limited usefulness on small flammable liquid fires, and cooking oil fires. Carbon Dioxide leaves no residue. Disadvantages
It is not suitable for outdoor use. Because it reduces oxygen it can be hazardous to humans in very confined spaces. CO2 extinguishers produce a loud noise when discharged, which may startle an inexperienced operator. Avoid discharging at people, frostbite to the eyes and face may occur. Avoid contact with metal components after use- "dry ice" may form on them.

Note for use near Switchboards
(Australian Standards 2444 section 4.4.2 Significant Swithboards)
A 5kg carbon dioxide extinguisher, or anther type of extinguisher having a minimum classification of 1A:E and fitted with a hose, shall be provided and shall be the extinguisher closest to the switchboard